The present invention relates to a magnetic disk drive and, in particular, to a flying head slider for use in the magnetic disk drive.
In the conventional magnetic disk drives, improvement in magnetic characteristic of a magnetic head and a recording medium or a magnetic disk and shortening of a distance between a gap tip of the magnetic head and a surface of the recording medium, that is, a magnetic spacing, were carried out for improving the recording density.
However, in the recent magnetic disk drives, in general, the physical minimum distance between the magnetic head and the magnetic recording medium has reached about 30 nm. This distance is comparable with the surface roughness of the recording medium. Under the circumstances, it is highly possible that reduction in flying height of the flying head slider induces a phenomenon of high-speed sliding contact between the flying head slider and the magnetic recording medium due to the limit in followability of the flying head slider against fluctuation of an air bearing function upon high-speed movement to a target position on the magnetic recording medium, that is, upon the so-called track seek, vibration of the flying head slider supporting system and vertical swelling of the magnetic recording medium.
These fluctuation factors of the flying height of the slider can be largely reduced by utilizing the negative pressure for the fluid bearing of the slider to enhance rigidity of the air bearing, thereby improving the medium followability of the slider.
Further, by achieving the sufficient rigidity based on the fluid bearing effect, the pressure load applied to the flying head slider by the suspension can be reduced. Moreover, since the take-off velocity of the slider is improved following enlargement of the air bearing surface, the durability can also be largely improved against the sliding contact upon CSS (contact/start/stop).
However, for adopting a read only head (which is so called MR head) utilizing a magneto-resistive effect, which holds the key to the high recording density and is excellent in S/N of read back signal, the flying height uniformity between inner and outer regions on the disk is more required than the case where the recording and reproduction are carried out using only a thin film head whose reproduction output characteristic depends on the rotation speed of the magnetic recording medium. This is caused by non-dependence of the reproduction output relative to the rotation speed, and hence, those regions where the probability of damage on the magnetic recording medium, namely, the magnetic disk is high due to the high-speed sliding contact, have been increased.
Referring to FIGS. 15 to 17, description will be made regarding typical flying head sliders utilizing the negative pressure, respectively. Specifically, FIG. 15 shows a two lane flying head slider 1, FIG. 16 shows a center rail flying head slider 1, and FIG. 17 shows a center pad flying head slider 1. In each of these figures, numeral 2 denotes a main recess, numerals 3 and 4 denoting a pair of side rails forming the main recess 2 on the slider 1, numeral 5 denoting a cross rail connecting between the side rails 3 and 4, and numeral 6 denoting a chamfer provided at an outer upper portion of the cross rail 5. In FIG. 16, numeral 7 denotes a center rail dividing the recess 2 into a pair of recesses 2a and 2b. Further, in FIG. 17, numeral 8 denotes a center pad disposed in the main recess 2 at a lower middle portion thereof.
In case of the two lane flying head slider 1 shown in FIG. 15, a magnetic head can be arranged at a radially outer side relative to a magnetic recording medium (not shown). Thus, it is excellent in recording capacity and, since the negative pressure can be fully ensured, it is suitable for the high-speed rotation. However, there are disadvantages that the limitation in design is large relative to the flying height uniformity and the flying attitude and that the minimum flying height fluctuation relative to disturbance is slightly greater.
On the other hand, in case of the center rail flying head slider 1 shown in FIG. 16 and the center pad flying head slider 1 shown in FIG. 17, it is easy to suppress the flying height fluctuation relative to disturbance and, since the limitation to the flying attitude is relaxed, it is easy to pursue the flying height uniformity.
However, since the side rails 3 and 4 are each shorter than the overall length of the slider 1, the positive pressures generated at air flow-out ends (trailing edges) of the side rails 3 and 4 are considerably lower than those in the two lane flying head slider shown in FIG. 15.
Particularly, since the positive pressure generated at the center pad 8, where the area is small and the flying height is small, frequently becomes more than twice the positive pressure generated at an air flow-out end of the two lane slider, it happens that a pressure differential at the air flow-out end reaches even 4 to 5 atm. Further, since the air flow velocity reaches 10 to 30 m/S, it is possible that moisture in the air or vaporized lubricant in the air for protecting the recording medium is liquefied due to the pressure fluctuation.
Further, it is also possible that the lubricant for protection of the recording medium adheres to the air bearing surface of the flying head slider upon CSS or upon the high-speed sliding contact with the magnetic recording medium and then moves along the air bearing surface due to the air flow so as to stay at the air flow-out end.
The foregoing phenomena may also occur similarly at an air flow-out end of the cross rail 5 which generates the negative pressure. In particular, although the positive pressure at this air flow-out end is not so high, since the negative pressure immediately after the cross rail 5 becomes maximum, a pressure differential is large. Further, there occur regions where the air flow velocity is small. Accordingly, a possibility is very high that introduced dust remains in such regions.
Specifically, although the flying head sliders utilizing the negative pressure have been predominant in recent years, since the pressure in the negative pressure generating region is lower than the ambient pressures, very small dust which is generated in the magnetic disk drive is liable to be sucked. Further, at the interface between the head and the disk in the foregoing near contact region, it is considered that the lubricant for the slider and the lubricant for the medium surface are constantly contacting with each other. Under the circumstances, there have been demands for flying head sliders which can prevent accumulation of the dust on the air bearing surface at a contact region thereof and at a small flying height region thereof near the contact region.